ean Rawson had passed through a nerve-racking experience. It was not a question of courage—Rawson had plenty of that—but there are times when a man's nervous system is shocked almost to insensibility by sheer horror. Not at once did he realize what was happening.

Perhaps it was the sound of pursuit that jarred him out of the fog clouding all his thoughts and perceptions. It was like the sound of fighting animals—cat-beasts—whose snarls had risen to screaming, squalling shrieks of rage. It was sheer beastliness, the din that echoed through that narrow passage.

Ahead of him the girl was running. She held a light in her hand. Soft wrappings of cloth hung loosely from her waist; like her golden hair, it was flung backward in the strong draft of air against which they were struggling. She was outlined clearly before the red, rock-like masses where her light was falling; she was running swiftly, gracefully, like a wild, woodland nymph.

Two men, their milk-white bodies naked but for the thick folds of their loin cloths, were beside Rawson, helping him along. Two others followed. And, by their haste and their odd whispered words of alarm, he knew that pursuit had not been expected; they must have thought to get away unobserved.

Rawson felt his strength returning. He shook himself free from those who tried to aid him. He was amazed at how easily he ran: his weight was a mere nothing; his efforts were expended in driving his body against the blast of wind. The air seemed dense, thick; he had almost the feeling of forcing himself through water.

Ahead of him the girl darted abruptly through a narrow crack in the wall. Rawson followed—and then began a wild race through a network of connecting passages, a vast labyrinth of caves, more like fractures in this strange red substance which Rawson could think of only as rock, for lack of a more accurate name, until at last there was no sound except that of their own hurrying feet.

hey stopped and stood panting in one of the wider passages. He heard nothing but the endless rush of the wind. For the first time Rawson became aware of his own almost naked condition.

The mole-men had prepared him for the sacrifice. They had decked him with a loin cloth of woven gold. It felt cold to the touch, and Rawson did not doubt its being made of fine threads of the precious metal. About his neck hung a gold chain with a heavy object suspended; he tore it off, and found again a representation of a golden sun. The copper priests had arrayed him to meet their fire-god, and again Rawson wondered at the emblem they employed.

"What in the name of the starlit heavens," he demanded silently of himself, "could this buried race know of the sun?"

The others were watching him. In the glow of that strange light held by the girl he saw them smiling. They were congratulating one another with odd, soft-syllabled words. And Rawson, ignorant of their tongue, was mute, when his whole soul cried out to thank them.

He gripped the hands of the men. They were as tall as himself, their gaze level with his own. Their faces were human, friendly; their eyes sparkled and smiled into his. Then he turned to the girl.

She had seen the method of greeting this stranger employed. She extended her hand—a white hand, slim, soft, cool. And Rawson, choking with emotion, knowing that here was the one who had first seen him and who had returned to save him, a stranger, bent low above that hand, held in his own so rough and burned, and pressed his lips to the slender fingers in a quick caress.

When he raised his head she was looking at him oddly; her eyes were deep, serious and unsmiling. He wondered if, blunderingly, he had offended her. He could not know; he did not know their customs.

Again the slim girlish figure turned; her jeweled breast-plates flashed as she led the others on where always the way led upward and the wind pressed against them unceasingly.

he White Ones wore sandals that seemed woven of glass. Rawson's bare feet were bruised and sore, for those narrower clefts had been paved only with broken fragments of the red walls. He moved less easily now. The heavy, beating air tired him; the lightness of his body made it all the more difficult to fight the steady wind. Still he followed the white figure of the girl where her light was flashing on endless walls of red.

In his ears a new sound was registering. Above the rush of the air, that now was soft and warm, a new note had risen to a hollow, unremitting roar. He knew that for some time he had been hearing it faintly. It grew louder, one long, steady, unchanging note, as they advanced. It was a deafening reverberation that seemed shaking the whole earth when they came at last to an open room.

It beat upon him thunderously. As deep as the deepest tone of a mighty organ, like a thousand gigantic organs welded in one, it roared and shook him through and through with its single note.

Exhausted by his wild flight, surrounded by this maelstrom of sound, he sank to the floor and let his laboring lungs have their way. But his eyes were searching the big room.

he great cave was too regularly formed to have had a natural origin. The light that the girl had carried gave only feeble illumination in so great a space that had so evidently been hollowed out of the solid red matter.

The light flashed here and there as the girl and her companions moved away. They were circling the room. Rawson saw the irregular outlines of entrances to many dark passages like the one through which they had come. The red rock-mass seemingly had been riven and torn, and apparently in front of each opening the white figures fought against the rush of outgoing air. Rawson felt the same current sweeping and whirling gustily about him.

Now his companions were across the room, and between him and them in the center of the floor he saw the mouth of a black well, a pit some twenty or more feet across. Directly above, where the red rock stuff formed a domed ceiling, he found a counterpart of the pit below—another great bore or open shaft, roughly circular. Apparently it went straight on up and was a continuation of that lower pit.

"This room was cut out," Rawson was thinking, "by the white people or the mole-men—Lord knows who, or when, or why. Cut out around this big shaft...."

His thoughts trailed off. Even thinking seemed impossible under the battering of the roaring noise that pounded about him. Then another thought pierced through the bedlam. He had found the source of the uproar.

hat upper shaft, the hole that went on up, must be plugged. There was no outlet that way, and this air that drove endlessly upward from the room must be coming from the lower shaft. It was striking up into that upper cavity.

An organ pipe, truly. But whence came the unending blast of air to keep that gigantic instrument in operation? Rawson dropped to his knees and crept slowly across the floor toward the pit. He must test his theory—see if that was where the air was driving in.

Just short of the brink he stopped. The girl had called—a cry of alarm. She was running swiftly toward him, circling the pit. And Rawson, as she tugged at him, trying to draw him back, knew that she had mistaken his motive. She had thought he was going to cast himself down.

He did not need to go farther. He was close to the edge. And now, even above that roaring sound he heard the rush of the column of air. He seated himself on the stone floor and smiled up at the girl reassuringly. Her eyes that had been dark with fear changed swiftly to a look so sweetly, beautifully tender that Dean Rawson found himself thrilled and shaken by an emotion that set his nerves to quivering even more than did the sonorous vibration from above.

Her companions had joined her. Dean saw her eyes regarding them steadily. Then, as if reaching some sudden final conclusion in her own mind, she dropped swiftly to her knees beside him, raised one of his hands in hers and pressed her soft lips against it.

And Dean, even had he known their language, could not in that moment have spoken. There had been something in the look of her eyes and the soft touch of her lips that of themselves went far beyond words.

"You darling," he was whispering softly to himself as the girl sprang to her feet and walked swiftly away, the others following.

"An angel, no less—down in this damned place!"

e wondered, as he watched the flickering light far across the room, what destination they could be bound for. Surely no one so radiantly beautiful could inhabit a world of endless dungeons like that where the mole-men lived. But if not that, then what? Where would their next journey take them? And in what direction would they go?

Again Rawson's thoughts were submerged beneath his own weariness. This air that beat about him had seemed cool after the terrific heat that drove in off the Lake of Fire. Now he realized that the air itself was hot. His one spurt of strength and energy had been expended.

He watched the men disappear into one of the passages, but he roused himself when they returned. They were clinging to a strange device, a metal cylinder that floated in air above their heads like a dirigible on end. It was about eight feet in diameter and some fourteen feet in height; both upper and lower ends were rounded. A cage of parallel bars enclosed it from end to end; like springs of steel they extended from top to bottom where they curved in and were attached to the rounded ends.

awson sat up quickly and stared in startled amazement at the thing glinting like polished aluminum in the light. And his engineer's mind responded as much to that smooth finish and the evident workmanship that had entered into the making of this thing as it did to the object itself.

The girl placed her light on the floor. She, too, reached up and gripped a bar of the protecting cage to which the others were holding. With her added weight and strength they drew it down almost to the floor. Rawson knew by their efforts that they were dealing with something actually buoyant, a metal balloon. One of the men, still putting his weight on the bars, reached in and opened a door in the smooth shell. He stepped inside, and a moment later the big shell dropped to the floor and, still vertical, stood on the lower rounded end of the protecting cage, rocking gently as the hot whirling wind hit it.

They were communicating among themselves by signs. Rawson saw them motioning. Speech was useless in that roaring, pandemonium-filled room.

She was motioning for him to follow. One of the men circled that central pit, came beside Rawson and helped him to his feet, steadying him as they crossed the room. The girl had entered the big metal shell. Dean saw the glow of her torch shining through the open doorway and through two other windows of crystal glass.

The big room had grown dimmer. The high ceiling was lost in murky shadows. All the room was dark save where that light struck upon walls and floor to make them glow blood-red. The waiting lighted shell seemed a haven of refuge. To get inside, close the door, lock out some of this unendurable, battering sound—it was all Rawson asked, all he could think.

The door closed. He was within the shell, standing on a smooth metal floor. The others were beside him. Dully he wondered what wild adventure was ahead.

e had expected—he hardly knew what. But there should have been machinery of some sort. If this weird balloon thing was actually to carry them, there must be some mechanism, some propelling power. And instead he saw nothing but the shining walls of the circular room and at the exact center, reaching from floor to ceiling, a six-inch metal post that thickened to a boxlike form on a level with his eyes. There was a plate on the side of that box, a cover, and clamps that held it in place, and on an adjoining side two little levers, one near the top of the box, the other near the bottom.

His one all-inclusive glance showed him bull's-eye windows in the ceiling. There were more of them in the floor. One curved bar, circling the room, was mounted on brackets against the wall. They were telling him by signs that he was to put his hands on it and hang on. One of the men was beside that central post. He too gripped at a projecting hand-hold. His other hand was on the lower lever.

Rawson knew his disappointment was unreasonable, but his weary mind was tired of mysteries. Some understandable bit of machinery would have been reassuring. And then in his next thought he asked himself what difference did it make. If this childish balloon thing were really capable of carrying them somewhere, what of it? It could only mean more of this hideous inner world that grew more unbearably fantastic with each new experience.

His life had been saved. True, but for what end? The girl's eyes were upon him, reading the expression on his face. She smiled encouragingly. Then Rawson's hands tightened upon the metal bar. The man who stood by the central post had moved one lever the merest trifle. Rawson felt the floor lifting beneath him. Then the shell, like a bubble of metal, pitched and tossed as the powerful air currents caught it.

is own lightness saved him from injury. He gripped the bar and held himself free of the wall. The round top of their strange craft grated against the domed roof. Then again the ship steadied and seemed motionless, and Rawson knew they had slipped up into the still air of that upper shaft.

For one wild instant, filled with impossible hope, Rawson saw this as a means of ascent to his own world. Then reason tore those wild hopes to shreds.

"It's closed up above," he thought. "It must be. That's why it sounded that way. That's why the air drove off through those side passages."

The next instant held no time for thought. Rawson's whole attention was concentrated upon the bar to which he clung. For, quicker than thought, the metal shell, the little cylindrical world in which he and these others were, fell swiftly beneath them.

His body twisted in mid-air. He knew the others were being thrown in the same manner. Then, what an instant before had been the ceiling was now a floor beneath his feet, pressing up against him and giving him weight—and by the whistling rush of the air that tore past their shell he knew they had fallen with marvelous swiftness straight down through the throat of that lower shaft.

And now what had been down was up. The ceiling of this strange room was now their floor, but Rawson was not deceived. "Acceleration," he said. "It's crowding us. The shell tends to fall faster than we do. It's like an elevator traveling downward at a swifter rate than a free falling body."

e had glimpsed the glassy-side of that well into which he knew they had been flung. He knew that the shrieks that filled the room time and again were caused by the touching of their shell's guiding and protecting bars against one glassy wall. Those sounds came always from the same side and Rawson found momentary satisfaction in his own understanding of the phenomenon.

"We're falling free," he argued within his own mind, "falling toward the center of the earth. And a falling body wouldn't follow a vertical course. It would tend to hug against one wall." And by that he knew something of their speed. The necessity for it was apparent a moment later.

Above his head the bull's-eyes pointing forward in the direction of their flight were faintly red. Swiftly they changed to crimson. Rawson was standing beside a window in the wall of their craft. That, too, grew quickly to an area of dazzling brightness. Slowly the heat struck in. The air in the little room was stifling. He saw the girl turn her head and give a sharp order.

The man by the central post responded with another slight movement of the lever. Beneath Rawson's feet the floor pressed upward in a surge of speed that bent his knees and bore him downward. Under his hands the rod to which he clung was hot. The shining walls were dimly glowing. They were being hurled through the very heart of hell....

nd then it was past. The crimson horror beyond those windows grew dull and then black. In the blunt nose of their craft a tiny crevice must have opened. The one who drove that projectile in its shrieking flight had touched another control that Rawson had not before seen. And with a piercing shriek a thin jet of cold air drove down into the hot room.

No wine could have been one-half so potent. That thin jet filled the room with buffeting whirlwinds that grew quickly cold.

Then their speed was checked. Abruptly Rawson was weightless, his body hanging in air, moved only as he moved his hand upon the bar. Only a few feet away was the body of the girl floating weightless like himself. The others were shouting loud words of satisfaction, but her face was turned toward Rawson, her eyes were smiling into his; while, outside the little shell that fell in meteor flight, were only shrieking winds and the blackness into which they plunged.